So I think I've figured out how to fix my problem with putting files on the distributed classpath by digging through the code Hadoop uses to process -libjars.
If I say DistributedCache.addFileToClassPath(hdfsFile,conf); then hdfsFile is added to the distributed cache, but doesn't show upon the classpath of the mappers or reducers, leading to crashings and burnings. But if I say DistributedCache.addFileToClassPath(new Path(hdfsFile.toUri().getPath()),conf); then hdfsFile *does* show up on the classpath, and my jobs run fine. So here's the thing: if I grab the code at this point in a debugger and check new Path(hdfsFile.toUri().getPath()).equals(hdfsFile) I *always* get true. That is, according to Path.equals(), hdfsFile and new Path(hdfsFile.toUri().getPath()) are semantically identical. So while I'm glad that I've got something working (and hopefully this will help anyone stuck in a similar place in the future), I'm incredibly confused as to *why* it works. Any ideas?
